# Standard library header <typeinfo>

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< cpp‎ | header

This header is part of the type support library.

### Classes

type_info | contains some type’s information, the class returned by the typeid operator (class)
bad_typeid | exception that is thrown if an argument in a typeid expression is null (class)
bad_cast | exception that is thrown by an invalid `dynamic_cast` expression, i.e. a cast of reference type fails (class)

### Synopsis

    namespace std {
      class type_info;
      class bad_cast;
      class bad_typeid;
    }

#### Class std::type_info

    namespace std {
      class type_info {
      public:
        virtual ~type_info();
        constexpr bool operator==(const type_info& rhs) const noexcept;
        bool before(const type_info& rhs) const noexcept;
        size_t hash_code() const noexcept;
        const char* name() const noexcept;

        type_info(const type_info&) = delete;                   // cannot be copied
        type_info& operator=(const type_info&) = delete;        // cannot be copied
      };
    }

#### Class std::bad_cast

    namespace std {
      class bad_cast : public exception {
      public:
        // see [exception] for the specification of the special member functions
        const char* what() const noexcept override;
      };
    }

#### Class std::bad_typeid

    namespace std {
      class bad_typeid : public exception {
      public:
        // see [exception] for the specification of the special member functions
        const char* what() const noexcept override;
      };
    }

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